1. Field of the Invention
This invention relates generally to a passenger vehicle occupant restraint system having an air bag module and, more particularly, to an air bag module having direct venting.
2. Background Art
Occupant restraint systems employing air bag modules are well known. During a collision of a predetermined magnitude, an air bag cushion is inflated by an inflator and is deployed in the vehicle for protection of the vehicle occupant. The air bag cushion is deployed at a high rate of speed and force optimized to protect a wide range of occupants under various conditions. There are, however, times when deploying an air bag cushion is not desirable, such as when a vehicle occupant is so close to the air bag that normal deployment of the air bag may cause injury to the occupant. An occupant that is too close to the air bag is said to be out of position. Various air bag module designs have been developed to reduce the amount of pressure and force caused by an air bag deployment to an out of place vehicle occupant. For example, some systems use vents on the air bag cushion that open and release gases generated by the inflator as the bag is deploying. However, these systems only control the rate and amount of inflation of the air bag cushion in a predetermined manner, but do not do so in response to the position of the occupant.
Another system disclosed in U.S. Pat. No. 6,206,408 uses vents on the air bag canister side wall that are initially open and slidingly close if no force is exerted on the deployment door. If force is exerted onto the deployment door, the vents remain open and the gas is vented therethrough, thereby thwarting deployment of the air bag cushion. However, this device is exceedingly complicated to manufacture requiring sliding mechanisms.
It would be desirable to have an occupant restraint system employing an air bag cushion that does not fully deploy when an occupant is out of position that is of a simple design.
It is an object of this invention to provide an occupant restraint system having an air bag module that does not fully deploy an air bag cushion if the vehicle occupant is out of position and is of a simple design.
Accordingly, this invention features an air bag module having direct venting of the air bag inflator gas into the ambient air if external force is exerted on the deployment door. If no external force is exerted on the deployment door, then the air bag cushion deploys normally through the deployment door and into the passenger compartment. The air bag module comprises an air bag canister having at least one side wall, the at least one side wall having at least one gas channel port to communicate with the ambient air, an air bag cushion attached to the canister, an inflator attached to the air bag canister for providing gas, a deployment door attached to the canister, a structural gas channel configured to communicate with the at least one gas channel port to provide venting of gas provided by the inflator to the ambient air if external force is applied to the deployment door, and a venting system connecting the structural gas channel to the at least one gas channel port and operative to prevent venting of gas through the gas channel port from the canister when the air bag cushion is in a substantially deployed condition.
In a first embodiment of the invention, the venting system comprises a non-porous fabric gas channel pivotally connecting the structural gas channel to the side wall proximate the gas channel port and a tether connecting the air bag cushion to the structural gas channel. During normal air bag cushion deployment, the air bag cushion is inflated by the inflator, thereby pulling the tether taut and pivoting the structural gas channel and the non-porous fabric gas channel to a position wherein the non-porous gas channel blocks the gas channel port and preventing gas from venting and loss of gas.
In a second embodiment of the present invention, the venting system comprises a plug located outside the canister and a pulling system to connect the plug to the air bag cushion. The plug could be connected directly to the air bag cushion by a plug tether, or indirectly by connecting the plug tether to an air bag-shaping tether. During normal deployment of the air bag cushion, the tether connected to the plug is made taut, thereby pulling the plug into the gas channel port and preventing any gas from venting therethrough.
In a third embodiment of the invention, the venting system comprises a non-porous fabric gas channel connecting the structural gas channel to the gas channel port, and a cinch tether attached to the air bag cushion and encircling the non-porous fabric gas channel, whereby deployment of the air bag cushion causes the cinch tether to cinch the non-porous fabric gas channel which prevents gas from venting through the gas channel port.